setup oracle correctly in stream writer

Author: mangalaman93

Diff for: levels.go

@@ -1573,8 +1573,8 @@ func (s *levelsController) close() error {
 }
 
 // get searches for a given key in all the levels of the LSM tree. It returns
-// key version <= the expected version (maxVs). If not found, it returns an empty
-// y.ValueStruct.
+// key version <= the expected version (version in key). If not found,
+// it returns an empty y.ValueStruct.
 func (s *levelsController) get(key []byte, maxVs y.ValueStruct, startLevel int) (
 	y.ValueStruct, error) {
 	if s.kv.IsClosed() {

Diff for: stream_writer.go

@@ -282,6 +282,11 @@ func (sw *StreamWriter) Flush() error {
 		if sw.db.orc != nil {
 			sw.db.orc.Stop()
 		}
+
+		if curMax := sw.db.orc.readTs(); curMax >= sw.maxVersion {
+			sw.maxVersion = curMax
+		}
+
 		sw.db.orc = newOracle(sw.db.opt)
 		sw.db.orc.nextTxnTs = sw.maxVersion
 		sw.db.orc.txnMark.Done(sw.maxVersion)

Diff for: stream_writer_test.go

@@ -750,4 +750,51 @@ func TestStreamWriterIncremental(t *testing.T) {
 			require.NoError(t, err)
 		})
 	})
+
+	t.Run("multiple incremental with older data first", func(t *testing.T) {
+		runBadgerTest(t, nil, func(t *testing.T, db *DB) {
+			buf := z.NewBuffer(10<<20, "test")
+			defer func() { require.NoError(t, buf.Release()) }()
+			KVToBuffer(&pb.KV{
+				Key:     []byte("a1"),
+				Value:   []byte("val1"),
+				Version: 11,
+			}, buf)
+			sw := db.NewStreamWriter()
+			require.NoError(t, sw.PrepareIncremental(), "sw.PrepareIncremental() failed")
+			require.NoError(t, sw.Write(buf), "sw.Write() failed")
+			require.NoError(t, sw.Flush(), "sw.Flush() failed")
+
+			buf = z.NewBuffer(10<<20, "test")
+			defer func() { require.NoError(t, buf.Release()) }()
+			KVToBuffer(&pb.KV{
+				Key:     []byte("a2"),
+				Value:   []byte("val2"),
+				Version: 9,
+			}, buf)
+			sw = db.NewStreamWriter()
+			require.NoError(t, sw.PrepareIncremental(), "sw.PrepareIncremental() failed")
+			require.NoError(t, sw.Write(buf), "sw.Write() failed")
+			require.NoError(t, sw.Flush(), "sw.Flush() failed")
+
+			// This will move the maxTs to 10 (earlier, without the fix)
+			require.NoError(t, db.Update(func(txn *Txn) error {
+				return txn.Set([]byte("a1"), []byte("val3"))
+			}))
+			// This will move the maxTs to 11 (earliler, without the fix)
+			require.NoError(t, db.Update(func(txn *Txn) error {
+				return txn.Set([]byte("a3"), []byte("val4"))
+			}))
+
+			// And now, the first write with val1 will resurface (without the fix)
+			require.NoError(t, db.View(func(txn *Txn) error {
+				item, err := txn.Get([]byte("a1"))
+				require.NoError(t, err)
+				val, err := item.ValueCopy(nil)
+				require.NoError(t, err)
+				require.Equal(t, "val3", string(val))
+				return nil
+			}))
+		})
+	})
 }